Hello
I make custom skis and snowboards specially for snowkiting races.
Length 215cm, Radius 150m, 100/94/100mm, hardness like DownHill skis, weight 2.3kg of one ski (4.6kg pair).
The geometry of kite skis is designed for racing, going on straight line with maximum speed, has the optimum hardness, providing a uniform diagram of the distribution of pressure on the edge, which ultimately makes it possible to avoid lateral slippage even on "bottled" ice. Skis for snowkiting CustomSkis do not break, perfectly keep the course, they can easily go against the wind, they are stable, they give an advantage in races before "downhill" skis and go on an equal footing with "speedski" skis, with less weight and length.

The edge in the beginning has the shape of the nose of the ship, this shape is better kept on hard ice.

I have been making skis for 5 years and have gained a lot of experience in making high quality kite skis. Athletes on my skis took up a lot of prizes at various competitions in Russia. You could see these skis on WISSA, TOKE, Ragnarock, etc.

The oldest of my skis for a kite is only 3-4 years old, up to 20 years is still far away =)
There have been occasions when skis cracked, but I found out all the nuances and eliminated the reasons for the subsequent models. But the base surface never delaminated on the ice.

I suppose several reasons for the delamination of DH skis on ice - a cheap, soft and thin base. Perhaps, when going on dry ice, the edge heats up so much that the base becomes softens, a thermal expansion of the base near the edge occurs, and the internal tension in the adhesive joint increases. And a permanent physical impact by the ice detaches a weakened base.

I use a thicker (1.7mm instead of standart 1.2mm) and stiffer base from IsoSport 7515. It is the hardest of all, which makes IsoSport (molecular mass 9.2 million), has a large heat capacity and a lower coefficient of temperature expansion. And in the glued state I can not tear it away with my hands.

I usually give a guarantee for 1 year for all my skis, but in view of the high cost of transportation, in case of delamination through my fault, I can reimburse expenses for skiservice, or make a new skis.

One problem I have had with DH skis, is that the base can melt/crack. I happens after prolonged use at high speed on hard ice. Do you use any kind of special base material to avoid this?

(I use ~20 year old FIS DH skis, so maybe age is a factor for my problems)

PStkk, in my experience there are a few factors that contribute to "base melt". First I think it's a misconception that the base is over heating and melting due to high temps generation at speed. I've had some skis that have run several thousand miles and never had a base delamination/melting issue. While others have failed within minutes. And not due to heat and high speed. My feeling is that most base failures start as a failure in base adhesion. Now maybe this failure is due to heat softening up the epoxy but my feeling is it is more likely due to a weak bond failing due to vibration generation on the hard ice OR overheating the ski edge while tuning and weakening the epoxy. (Easily avoided by hand tuning) Or a combination of both.

All it takes is a microscopic gap to develop in the junction of the base material and edge material. Once this begins, ice will begin to get under the base material and build up. This forces the base material to delam and crown which allows more ice, which causes more delam and so on. The base material, depending on how high the molecular weight is, will heat up, soften and tear. Given the rate of speed that gravity powered speed skiers achieve without "melting" thier bases, I find it unlikely that our base failures are due to heat.

We found about 10-12 years ago that "feathering" the edges when stopping or turning on hard ice greatly reduces the likelihood of base failure. This video shows this a bit...

This all said, some skis are better suited than others. Given that none of the alpine skis we ride were intended to be used in such a manner. In my experience, Salomons are the most durable out there. Again, I've had several pairs of DH (≥45m) skis that have run literally thousands of miles on glass ice without issue. While on the other hand I've had Rossignols that failed within 15 minutes on hard ice.

Sometimes it's just luck and you get a ski that isn't built well. Sometimes it's technique and not taking care to protect the ski while riding. But we see very few base failures here due to poor construction. Even on old skis that don't even have sintered bases. My favorite ski was a 222cm Yamaha DH. 30 year old ski and ran it for about 2300 miles before the base failed. My guess is that the bond failed as a result of the edge heating while tuning. The edges were so thin at that point hand tuning was the only way to sharpen them without too much heat. But I was lazy and we have a side edger machine so I probably screwed them.

I think Vladimir is maybe on the right track with his choice of base material. But maybe not? This thicker material will affect the flex of the ski as well as dampening properties. Which may be counter productive as it will provide less give and be prone to the affects of vibration. Then again, maybe it will be less prone to failing at the base/edge interface which I honestly think is where the trouble starts.

Yes, I do not know at 100%, may be it is possible because of microcracks, when water penetrates into them, and because of the friction of the edge there is heat, which makes a multiple transition through the freezing point. Usually this kind of breaks the iron pipes in winter =)

Just a little water allowed to enter a ski and freeze will cause damage. It can split rock, burst pipes and kill skis. I used to do a lot of ski repairs. Some of them were simple, very basic edge delams that were minor when discovered at the end of the day. But the client leaves the ski out in the car over night, water freezes, expands and ends up with a much bigger repair job for me.

On the ice, we may be forcing water into the ski, may even be micro ice shavings. By they pack up or expand either way and you end up with an unusable edge as the base bulge interferes with edge contact. We've experimented with various repair methods. What has worked for me on the hill does not work on ice. The forces and environmental elements are very different. Close to a world cup super G course but much longer exposure. LAst season I tried a concrete epoxy as a filler. Cut away the damaged material and fill. Doesn't seem to cause signifigant drag and the repairs I did lasted about 300 miles of abuse (actually trying to force it to fail for the first 80-90 miles then just skied normally)

Portions of the repair started to come out. But very small and without any real affect to the usefulness of the ski.

By the way, during the experiments, I did very crooked skis, with slots, etc., but they still work (Mileage more than 1000 km), although there were a delams of bundles between the edging and the core, but the base did not come off at all.
Most likely, if the base is peeling off the edge, the surface preparation technology was broken: the edge was not degreased, or there was oil mist from the vacuum pumps in the air, or something like that. And everything else (heating, water, etc.) is already secondary.